Telephone system



Oct. 11, 1938. v H E I 2,133,055

TELEPHONE SYSTEM Filed Sept. 14, 1956 INVENTOR MAR TINHZBZL Y f A 701w YS Patented Oct. 11, 1938 UNITED TA ES I TELEPHONE SYSTEM I g Martin Hebel, Oberbayern, Germany Application September 14, 1936, Serial No. 1004;":1 1 a a In-Germany February 12, 1936 12 Glaims." (01. 179-16) The invention relatesto a circuit arrangement for selector operated telephone. installations working in conjunction with a number of. ex-, changes connected'to each other by. inductively coupled two-wire ;trunks. In circuit arrangements of this kind, repeaters are arrangedat the ends of the trunkline by means of which the line is inductivelyconnected to the-circuit inthe exchange. These repeaters comprise switch means 1 which transfer the outgoing andincomingimpulses respectively to the line and tothe circuit in the exchange I It is already known-to connectithe switch means belongingto the grepeatersatithe outgoing end, of

1, the line and serving to transfer the current impulses to the line permanently to-one wire-of-{the speech circuit in the exchangeand to construct the switch means which'receive backward signals over the'line insuch a manner that these are first of these switch meansare connected so as to transmit the signals'solely over one of the wires.

of the speech line of the exchange at the incom- 5 ing end and thesecond are connected to the other wire so that incoming signalsare transmitted exclusively over one wire and backward signals exclusively over the other. Furthermore, the switch means provided for the transmission of the back- 40 ward signals arearr-anged so as to co-operate with an auxiliary relay in such a manner that at the beginning and at the end of each backwardsignal received; over a wire they transmit an alternating current impulse over the trunk. With this construction of the repeater'at the incoming end of the line, it is possible for signals in onedirection in the exchanges to run always over, the one and;

same speech wire, andsignals in the other direction to run always over the other speech wire, so 50 thateven in'thecase of connections made through a series of exchanges, the repeater at the incomline. 55 current at the beginning andat-the end 7, and

of each backward signal makes it possibleto repeat ov er' theline by, means of short alternating current impulses all important information from at theincorning end are inaccessible anddurin g whichtherepeater. at the outgoing end must be preventedifrombeing. seized.

In order that the invention may be. thoroughly understood and be more readily carried into effect, an example of: construction in accordance therewith will nowbe described with referencelto the accompanying. drawing, in which:-- i Figure '1 illustrates a circuit diagramfor an arrangement in accordance. with the invention,

Figure 2 a modification of the arrangement of When the. repeater Ul at the outgoingend of the trunk VL- is seized, the relay [0 is energized by means ofthe auxiliary. c-wire. The contact I cl closes the circuit for a slow to-respond relay I U; and the contact I02 the circuitfor the. transmitting relay" IS whilethe contact 103- ensures the energization of the relay IC. The relay ls responds and, by means ofdts contactslsl. and I82, connects the source of. alternating current IQ to the-linefor the duration of thedelayin theresponse of therelay III. Assoon as this relay IU pulls up, the circuitot the relay IS is interrupted at thecontact l ul. The alternating current impulse thus sent out through;the-line influences the relay 2Ein the repeater U2'at the incoming end of the trunk and the relay 2E energizes an auxiliary relay 2A. by meansof its contact 2e. Therelay 2A, by means ofits contact 2a3, energizes a slow-to-releaserelay 2V and, by means-of its contact'2a2, closes thecircuit for the seizing 40 relay 2C,which,.by means of the contact 20!, closes a holding circuit for itself. The short cir- CIlitf 'fOX a. relay H isremoved by meansofthe contact 2e2. and the relay H responds and, by means of -its.contact.h-| ,preparesa short circuit for the relay-2C. By'means-of the contact 203 of the relay-2C,' the. seizing relay 3C for thenext selector (in the present c'ase, thefinal selector) 'is energized: ,By'means of the contact 204, the

energizing-circuit for a relay 2U is also closed, whichrelay prepares, at its contact 211], the retrans-mission of; the current impulses. I

The current impulses-sent out by the calling station-:a're. received through the a-wire by the relay" IA. The transmitting'relay IS is energized s I contact 20.

for the duration of each current impulse by means of the contact IaI and connects the trunk line to the source of alternating current IQ. At the incoming end of the trunk, these alternating current impulses are received by the relay 2E and are retransmitted over the a-wire by the auxiliary relay 2A through the" agency of. the The relay 3A of the final selector receives these current impulses and sets the final selector in the usual manner.

When the called subscriber removes his receiver, the relay 3Y responds and closes its con-' tact 311. In this way, theb-wire of the speech line remains connected to the source of'current' for the length of time during which the receiver is removed and the relay K in the repeater U2 is energized by its winding I. By means I of its contact kl, the relay K closes a circuit through its own holding winding II. This circuit runs;

the relay 2S is interrupted bymeans of the con tact II and thus stops the transmission of alter- 71y so that it depends upon the normal position energization of the relay K is, however. maintained by its winding KI which, when the contact l3-is opened, is connected through its contact 703 to the b line and thus remains under the influence of the contact 3y. v,

In the repeaterUI, therelay IE is energized by the received alternating current impulse which, by meansof its contact Ie, closesthe following circuit for a relay IY: V

resistance, contacts Ie, IzvI, relay IY, contact Is3, 1 V

The relay IY is .energized in this circuit and by means of its contact ly2, prepares the energization, of therelay :IX. When the'relay IE 7 M2, Iy2, relay IX, contact Is3,

The relay IX is energized in this circuit. The make-beforeebreak contact Iss3 switches the holding circuit'for the relay IY over appropriateof the contact le. The contact I x2 closes a hold ing circuit for, the relay, IX. The relay IY thus remains energized and by means of its contact I113, connects the'b-wire leading to the preceding selector to the source of current. The current flowing through the b-wire may influence a metering deviceor any, devices which indicate thatfthe called subscriber has removed his receiven set, the .relay -3Y releasesand the b-wireof the final selectorbecomes devoid-of current. Also,

' the relay K in the repeater U2 releases and by means of the contact k2, closes the circuit for Icontact kl interrupts the circuit for"the' relay L cuit for the relay 2S. alternating current impulse .will'agai'n beisent to the line as long as the relay ZS'remains energized, and will energize the relay IE. When the contact Ie is re- The contact Z2 short' circuits VVhen'the called subscriber restores hishand' lithe relay IE drops as does the relay IX. By the release of the relay IY, the b-wire running to the preceding selector is again devoid of current. On release of the relay IX, the switch device formed by the relays IX and IY is again returned into the normal position. Q

When the calling subscriber replaces his receiver, the relay becomes devoid of current. The circuit for the relay IU is interrupted at the contact IcI and the circuit for the transmitting relay IS is closed at the contact I 02 for the time during which the relay IU is released. The relay IS sends a longer alternating current impulse through the line which is received in the repeater U2 bythe relay 2E. The auxiliary relay 2A which is dependent upon the relay 2E short circuits the relay 2G by means of'its' contact 202 so that the latter releases. The relay I-I, duringthis time, remains attracted and prevents an immediate re-energization of the relay 2C. 7

When the relay 2C has released, the contact 203 interrupts the circuit -for the relay '30 so that-the final selector is released. 7 On release of the relay 30, the contact v3c connects the bwire' of the final selector to the source of current through an oiT-normal contact lco of the current impulse in the manner already described and by means of its contact I yd, interrupts the seizing circuit for the relay IC and thus prevents the repeater UI from being seized. I

. When the final selector reaches its normal position, the off-normal contact 700 opens and makes the b-wire devoid of current; In 'the repeater U2, the relays K and L release in succession as described so that the transmitting relay 2S sends man alternating current impulse. 'Therelays IX and IY in the repeater UI release on recep tion of this alternating current'impulse so that this repeater can again be seized. v

If the calling subscriber replaces his receiver before the called subscriber does so, the release impulse is immediately sent by the repeater UI to therepeater U2. This takes place while the relay 3Y of the final selector and, therefore, the relays K and L of the'rep eater U2 and the relays I Y and IX of the repeater UI are still energized to indicate that the called subscribers receiveris removed. In order to ensure the transmission of the indication that backward signals cannot be transmitted which requires the switching devicesK, L and IX, IY to co-operate with certainty in phase with each other,- both switching devices are positively returned into'the normal position. The contact I53 interrupts'the circuits of therelays IX and IY in the repeater III. In

a the repeater U2, the b-wire is interrupted by the contact 21; of the relay 2V, the energization of which is dependent upon the condition of "the auxiliary relay A and thus the relays K and L "through then-wire.

ensures that after transmission of the alternating our-rent'impulse in the direction in which the connection is being made, the backward signal {takes place in the right .form.

When the line is seized by a particularservice station suoh-asa toll exchange, the transmission 1 of the various switching impulses-can be efiected ashas beendescribed. The change-over for the difierent'working of the line selector can be efie'c'ted in -a known but not illustrated manner by transmission-of a seizing impulse differing from the usual seizing impulse. The switching m'eas ures carried out by the toll operator during a connection are then transmitted, as is the numericalf current impulse emission, through thea- 'wire and are retransmitted in the repeater U2 For repetition of the ringing or for switching through to-a seized line and like measures, it is thus only necessary to transmit an alternating current impulse through the trunk line. Likewise, the backward signals effect'ed through the final selector are all repeated through the b wire to'the repeater U2, and are converted by the switching device K, L. The

fsw itching device IX, IY of the repeater 'UI' then retransmits this switching criterion according to its signification through the b-wire to the particul-ar service station.

, 'Itis clear that the switching device K, L is'so constructed that on its actuation it always-causes an-alternating current impulse of a particular length to be sent out. In this way, the correct response of the switching device is ensured even if it is influenced only for a short period. Energization of the relay L is alsoensured, even when 1 a ing device IX, IY which differs from that shown Figure 1 only by the introduction of an additional slowi-to-re spond relay IW which,'on its response, positively interrupts thecircuits for the relays IX and IY. Whenusing such an arrangement, the relay'L of the repeater U2 is so designed that its delay in releasing isgreater than its delay in responding. On release of the relays K and L, that is to say, at the end of a switching step transmitted through the -b-wire, a longer alternating current impulse is thus' always sent through the line which, by the energization of the relay IW, resets the relays IX and IY positively and accurately into the normal position.

Also with the use of the switching device for suprangement isarran ged to cope with traflfic in both' directions.

Iti's clear "from the described example that the switching. steps transmitted separately according to their direction through the various speech wiresin thelocal circuitsof. the various ex' i chan'ges, can be effected by currents in the same direction; N0 switch me'an'sare, therefore, necessaryfto :make it possible for the speech lines to be connected to different sources of current.

Iclaim: LA telephone system comprising two exchanges with speech lines, a trunk'line between "said exchanges, repeaters at the two ends or said trimkflineconnecting said trunk line inductively tdsa'idexdhanges, means associated with :said repeater at the incoming end of said I trunk line for receiving abackward-impulse over a speech wire and retransmitting said impulse in the 'form; of two impulses through said trunk line, means associated with said repeater at the outgoing end of said trunk line for converting two impulses received over said trunk line to one impulse and for retransmitting said impulse over a'speechwire, means associated with said repeater at the outgoing end of said trunk line for transmitting impulses through said trunk line, and means associated with both repeaters for positively actuating in phase said impulse doubling and halving means on transmission of impulses from the outgoing to the incoming repeater.

2. A telephone system comprising two exsaid exchanges, repeaters at the two ends of said trunk line' connecting said trunk line inductively to said exchanges, means associated withsa'id repeater at the incoming end of said trunk line for receiving a backward impulse over a speech wire'and retransmitting said impulse in the form; of two impulses through said trunk line, means associated with said'repeater at the outgoing end of said trunk line for converting two impulses received over said trunk line to one impulse and 'for retransmitting said impulse over a-speech wire, means associated with said repeater at the outgoing end of said trunk line {for transmitting impulses through said trunk line and means associated with both repeaters for positively-setting into the normal position said impulse doubling and halving'means on transmission of impulses from the outgoing to the incoming repeater. v

3.11 telephone system comprising two airchanges with speech'lines, a trunk line between said exchanges, repeaters at the two ends of said trunk line connecting said trunk line inductivelyt'o said exchanges, means associated with said repeater at the incoming end of said trunk line for receiving a backward impulse over a speech wlrea-nd retransmitting said impulse in the form of two-impulses through said trunk linefmeans associated with said repeater at-the outgoing andof said trunk line ior converting y twoimpulses received over said trunk line to one impulse and for retransmitting said impulse over a speechwire, means associated with said repeater atthe outgoing end of said trunk line i for transmittingimpulses through said trunk line and means associated with both repeaters for foutg oin'grepeater.

.4: A telephone installation comprising two exchanges with speech lines, a trunk line-between said exchanges, repeaters at the two ends 'ofsa-id'trunk line connecting said trunk-line infductively to-the speech lines ofsaid exchanges, said incoming repeater being provided with a changes with speech lines, a trunk line between relay connected to one wire of said speech line 01" said exchange, a marginal relay controlled by said,

, over said speech wire and a further alternating current impulse is transmitted when current ceases to flow over said speech wire, said outgoing repeater comprising means'for receiving alternating current impulses transmitted through said trunk line, a relay controlled by said means andactuated at the beginning of the first received impulse, an auxiliary relay controlled by said means and actuated at the end of the first received impulse; said auxiliary relay being adapted to guard the energization of said first named relay, both relays being de-energized on the reception of a second alternating current impulse, said first named relay being adapted on its actuation to transmit currentthrough :a wire "of the speech line of saidexchange at the outgoing end of said trunk line corresponding to said wire of the speech line of the exchange 'at the incoming end over which the current actuating said means at'the incoming end flows. 7

5.A telephone system comprising two ex-l changes with two-wire speech lines, a trunk line between saidexchanges, a repeater at each'end of said'trunk 'lineconnecting said trnnk' line to one of said exchanges, means associated with said repeater attheoutgoing end 01 said trunk line, connected to only one of the twowires of a speech line and adapted to receive impulses I over said wire and to retransmit said impulses over said trunk line,'means associated with said repeater at the incoming end of said trunk line adaptedhto receive impulses over said trunk line and to retransmit said impulses over that of the two wires of a speech line corresponding to the wire to which said impulse receiving means at the outgoing end of said trunk line is connected, means associated with the repeaterat the incoming end of said trunk lineandl con= nected to the other wire of said, speech line for receiving backward signals over said wire and transmitting saidsignals over said'trunk line and means associated withsaid repeater at the outgoing end of said trunk line for receiving said backward signals over said trunk line and, transmitting said signals over that of the two wires oia speech line corresponding to the wire to which said'backward signal repeating means at the incoming end of the trunk line is connected.

6- A telephone system as claimed in claim 5,

in which the repeater at the incoming end of the trunk line comprises an auxiliary relay cooperating with said backward signal repeating means for transmitting, an impulse over said trunk line both at' the beginning and atth'e end 'of' a'backward signal received over the 'wire of said speech line; v v

7. A telephonesystem comprising-twee};- changes'with' two-wire speech lines, a trunk, line between said exchanges, a repeater at each end of said trunk line connecting'said trunk line to said goingpend'of said trunk line'for receiving said impulses and for starting the trans'missionof a backward signalton the'receptic-n of the first of said impulses and stopping the transmission of said signal on the reception of the second of said impulses, said last mentioned signal being transmitted over that of the two wires of a speech line corresponding to the wire to which said backward signal receiving means at theincoming end of the trunk line is connected' 8. A telephone system as claimed in claim 7, in

v which said repeaters connect the two ends of said trunk line inductively to the speech lines of said exchanges and in which said impulse transmitting means are adapted to transmit alternating current impulses.

9. A telephone system as claimed in claim '7 comprising also a slow acting relay at the incoming end of said trunk line and in which said backward signal transmitting means at the incoming end of said trunk line are provided with two windin sone connected to one of said speech line Wires and the other connected in series with said slow acting relay and adapted to be energized upon actuation of said transmitting means by a backward signal over said lastmentioned wire.

10. A telephone system comprising a pair of exchanges, a speechline in each of said exchanges, a trunk line connecting said exchanges trunk line, a slow acting relay in the repeater at the incoming end connected in series with the other winding of said backward signal receiving relay, actuated through a further working contact of said backward signal receiving relay, having a normal contact connected in parallel with said first mentioned iworking contact and having a contact adapted'to short circuit said last mentioned winding, a transmitting relay in the repeater at theincoming end adapted to be actuated by said backward signal receiving relay for the transmission of an impulse at the beginning and an impulse at the end of a backward signal received over the trunk line and means associated with the repeater at the outgoing end adapted to receive said impulses and to start the transmission of a backward signal on reception of the first of said impulses and to stop the transmission thereof on reception of the second, said transmission being effected over that wire of a speech line corresponding to the wire to which said backward signal receiving relay at the incoming end is connected. t

11. 'A telephone system comprising a pair of exchanges, a'speech. line in each of said exchanges, atrunk lineconnecting said, exchanges to each other, a repeater at the end of said trunk line in each of said exchanges, a backward signal receiving relay in the repeater at the incoming end of said trunk line having'two windings and a working contact through which one or" said windings is connected to only one wire of the speech line in the exchange at, the incoming end of said trunk line, a slow acting relay in the repeater at the incoming endconnected in series with the other winding of said backward signal receiving relay, actuated through a further worka ing contact of said backward signal receiving relay, having anormal contact connected in par-" allel with said first mentioned working contact and a contact adapted to short circuit said last mentioned winding, a transmitting relay in the repeater at the incoming end adapted to transmit an alternating current impulse through said trunk line at each actuation, an energizing circuit for said transmitting relay comprising a make and break contact of said backward signal receiving relay and a make and break contact of said slow acting relay adapted to close said circuit at each actuation of said backward signal receiving relay until the following actuation of the said slow acting relay, and means associated with the repeater at the outgoing end adapted to receive said impulses and to start the transmission of a backward signal o'nreception of the first of said impulses and to stop the transmission thereof on reception of the second, said transmission being effected over that wire of a speech line corresponding to the wire to which said said line inductively to said exchanges, switch. means in the exchange at the incoming end of said trunk line, means controlled by said switch means for transmitting a calling back signal through a wire of the speech line at the incoming end, means associated with the repeater at themcoming end connected to said wire adapted to cause said repeater on reception of said calling back signal to transmit two impulses through said trunk line and means associated with the repeater at the outgoing end adapted on reception or the first of said impulses to preclude seizure of said repeater from the outgoing exchange and to reallow such seizure on reception of the second of said impulses.

' MARTIN HEBEL' 

